Field
The present disclosure generally relates to a method and apparatus for forming interconnects and other conductive features in the fabrication of integrated circuits and other electronic devices. Specifically, the present disclosure relates to a method and apparatus for forming a protective layer resistant to halogen based precursors.
Description of the Related Art
As the structure size of integrated circuit (IC) devices is scaled down to sub-quarter micron dimensions, electrical resistance, and current densities have become an area for concern and improvement. Multilevel interconnect technology provides the conductive paths throughout an IC device, and are formed in high aspect ratio features including contacts, plugs, vias, lines, wires, and other features. A typical method for forming an interconnect on a substrate includes depositing one or more layers, etching at least one of the layer(s) to form one or more features, depositing a barrier layer in the feature(s), and depositing one or more layers to fill the feature. Typically, a feature is formed within a dielectric material disposed between a lower conductive layer and an upper conductive layer. The interconnect is formed within the feature to link the upper and lower conductive layers. Reliable formation of these interconnect features is important to the production of the circuits and the continued effort to increase circuit density and quality on individual substrates.
Copper is a choice metal for filling sub-micron high aspect ratio interconnect features because copper and its alloys have lower resisitivities than aluminum. However, copper diffuses more readily into surrounding materials and can after the electronic device characteristics of the adjacent layers. The diffused copper can form a conductive path between layers thereby reducing the reliability of the overall circuit and may even result in device failure. Hence, barrier layers are deposited prior to copper metallization to prevent or impede diffusion of copper atoms. Barrier layers typically are refractory metals such as tungsten, titanium, tantalum, and nitrides thereof, which all have a greater density than copper.
Halogen based precursors, such as chlorine and fluorine, aid in depositing a uniform barrier layer as compared to non-halogen based precursors. Halogen based precursors, however, may corrode the copper filling the high aspect ratio interconnect. This results in formation of various copper compounds that are difficult to remove from the substrate due to low volatility. Thus, the copper may corrode resulting in a reduction in reliability and loss of yield.
Therefore, there is a need to prevent adverse reaction between halogen based precursors and copper material comprising an interconnect.